Organ donor Hu Jie, 25, a Chinese migrant worker, who changed his mind about selling his kidney but could not escape surgery once he had signed for it. Photograph: Nicola Davison

The illegal trade in kidneys has risen to such a level that an estimated 10,000 black market operations involving purchased human organs now take place annually, or more than one an hour, World Health Organisation experts have revealed.

Evidence collected by a worldwide network of doctors shows that traffickers are defying laws intended to curtail their activities and are cashing in on rising international demand for replacement kidneys driven by the increase in diabetes and other diseases.

Patients, many of whom will go to China, India or Pakistan for surgery, can pay up to $200,000 (nearly £128,000) for a kidney to gangs who harvest organs from vulnerable, desperate people, sometimes for as little as $5,000.

The vast sums to be made by both traffickers and surgeons have been underlined by the arrest by Israeli police last week of 10 people, including a doctor, suspected of belonging to an international organ trafficking ring and of committing extortion, tax fraud and grievous bodily harm. Other illicit organ trafficking rings have been uncovered in India and Pakistan.

The Guardian contacted an organ broker in China who advertised his services under the slogan, "Donate a kidney, buy the new iPad!" He offered £2,500 for a kidney and said the operation could be performed within 10 days.

The resurgence of trafficking has prompted the WHO to suggest that humanity itself is being undermined by the vast profits involved and the division between poor people who undergo "amputation" for cash and the wealthy sick who sustain the body parts trade.

"The illegal trade worldwide was falling back in about 2006-07 – there was a decrease in 'transplant tourism'," said Luc Noel, a doctor and WHO official who runs a unit monitoring trends in legitimate and underground donations and transplants of human organs. But he added: "The trade may well be increasing again. There have been recent signs that that may well be the case. There is a growing need for transplants and big profits to be made. It's ever growing, it's a constant struggle. The stakes are so big, the profit that can be made so huge, that the temptation is out there."

Lack of law enforcement in some countries, and lack of laws in others, mean that those offering financial incentives to poor people to part with a kidney have it too easy, Noel said.

Kidneys make up 75% of the global illicit trade in organs, Noel estimates. Rising rates of diabetes, high blood pressure and heart problems are causing demand for kidneys to far outstrip supply.

Data from the WHO shows that of the 106,879 solid organs known to have been transplanted in 95 member states in 2010 (legally and illegally), about 73,179 (68.5%) were kidneys. But those 106,879 operations satisfied just 10% of the global need, the WHO said.

The organisation does not know how many cases involved the organ being obtained legitimately from a deceased donor or living donor such as a friend or relative of the recipient.

But Noel believes that one in 10 of those 106,879 organs was probably procured by black marketeers. If so, that would mean that organ gangs profited almost 11,000 times in 2010.

Proof of illegal trafficking is being collected by networks of doctors in various countries known as "custodian groups". The groups work to support the Declaration of Istanbul, the 2008 statement against global organ exploitation that was agreed by almost 100 nations.

Made up of hospital specialists who treat patients with end-stage kidney failure who survive on dialysis, and surgeons who operate on those lucky enough to get a new kidney, the groups monitor reports of black market activity in their own country or involving compatriots abroad.

A medical source with knowledge of the situation said: "While commercial transplantation is now forbidden by law in China, that's difficult to enforce; there's been a resurgence there in the last two or three years.

"Foreigners from the Middle East, Asia and sometimes Europe come and are paying $100,000 to $200,000 for a transplant. Often they are Chinese expats or patients of Chinese descent."

Some of China's army hospitals were believed to be carrying out the transplants, the source added.

The persistence of the trade is embarrassing for China. The health ministry in Beijing has outlawed it and has also promised to stop harvesting organs from executed prisoners by 2017, a practice that has brought international condemnation.

John Feehally, a professor of renal medicine at University Hospitals of Leicester NHS trust, said: "Since the Declaration of Istanbul the law on trafficking has been changed in the Philippines – which was one of the centres of transplant tourism – and the Chinese government realises that things have to change." Feehally is also president of the International Society of Nephrology, which represents 10,000 specialist kidney doctors worldwide. "Trafficking is still continuing – it's likely that it is increasing," he said. "We know of countries in Asia, and also in eastern Europe, which provide a market so that people who need a kidney can go there and buy one."

The key issue, Feehally said, was exploitation. "You are exploiting a donor if they are very poor and you are giving them a very small amount of money and no doctor is caring for them afterwards, which is what happens.

"The people who gain are the rich transplant patients who can afford to buy a kidney, the doctors and hospital administrators, and the middlemen, the traffickers. It's absolutely wrong, morally wrong."

Noel wants countries to defeat the traffickers by maximising the supply of organs from deceased and living donors, and encouraging healthy lifestyles to stop people getting conditions such as diabetes in the first place.

• This article was amended on 31 May 2012. In the original, the forename of Prof John Feehally was incorrectly given as Jim.